Just in case that link doesn’t work at some point, here is paragraph 3: SALUTING. All Marine Corps Veterans will NOT execute this salute as part of the strict Marine Corps tradition (see ALMARS 052:08). The Defense Authorization Act of 2000 and subsequent years authorizes military veterans in civilian clothes to render the hand salute as the flag passes or for the Star Spangled Banner. Again, nothing to get bent out of shape about. This is my (permanent) physical difference. The appearance of my hand is the same as everyone around me unless you look very, very closely. From my first salute in Air Force JROTC, through my time at New Mexico Military Institute, and then during my career in the Air Force, my thumb was never addressed except for once. How do I hold a hand salute for longer than 60 seconds? My thumb buckles a little and draws back. It doesn’t stay straight without considerable effort and even then my hand tires within a minute or so. My second story is about the thumb on my right hand. This was a temporary physical difference. It took a couple of years, but he was able to use his hand eventually. I eventually found out that his doctors stated that he had to wait until his hand finished drawing up before they could treat the condition. What was his problem? Dupuytren Contracture. My reply was that we cannot help medical conditions and points would not be taken off. One of the team members was not able to salute properly (similar to the female officer above) and I was asked if that would cause the team to be marked down. Let me tell you about an honor guard competition I judged in 2009. It’s most likely her (permanent of temporary) physical difference and since law enforcement officers do not have strict guidelines on rendering the hand salute, she probably has continued in her job just fine.
You see the female officer rendering a hand salute that is not perfectly straight.
The two types of authorized salutes used in the US military (not for ceremonial drill) How to Salute